Designers of refracting telescopes figured out, for one, that by using two different kinds of glass together in the objective lens, they could cause the red and blue ends of the spectrum to ...

When you look at the night sky, do you ever wonder what's going on out there? On a clear night with a dark sky, if moonlight doesn't wash it out, sometimes you can see the arc of the Milky Way.

An optical telescope receives and refracts visible light using an arrangement of lenses. observe visible light from space. Small ones allow amateurs to view the night sky relatively cheaply but ...